[Biology Class Notes] on Competitive Exclusion Principle Pdf

The Competitive Exclusion Principle was first proposed by G.F Gause. According to the principle he stated, those species which compete for the same resources cannot coexist. This principle is also known as Gause’s law. By this law, it is stated that one population will drive off the other one. The one remaining in the system definitely has strong adapting capacity. Let’s suppose that, if a forest’s maximum population is carnivores, then definitely in that area there will be a shortage of food. This will cause scarcity of food among animals which causes competition among the animals due to competition of best survival. The one who has strong power will definitely defeat the weaker section and by the passage of time, the weaker section will get eliminated. 

One more example of competitive exclusion is, how red squirrels replaced the grey squirrels in Britain?  Suddenly the number of squirrels decreased in Britain because of the disappearance of hazelnuts, which led to competitive exclusion. Whereas gray squirrels adapted to the situation and replaced the red squirrels eventually. 

History:

The competitive exclusion principle was initially given by Georgii Gause, but basically, he never formulated this principle. This principle was already there in Darwin’s theory of natural selection. This principle revolves between a priori and experimental truth. 

Prediction: 

The competitive exclusion principle is also predicted by mathematical and theoretical models like Lotka-Volterra medals of competition. But because of its weak reasons, competition exclusion is hardly observed in natural ecosystems, and many biological communities appear to violate Gause’s law. One of the best-known examples is the so-called “paradox” of the plankton. All plankton species survive on a very limited number of resources, mainly on solar energy, only a very small number of plankton species should be able to coexist on these resources. 

 

Types of Competition In Competitive Exclusion:

There are mainly two types of competitions in the competitive exclusion principle:

1. Interspecific Competition: In this, competition takes place between organisms of different species.

2. Intraspecific Competition: In this, competition takes place between organisms of the same species. 

Sub-Types of Competitions:

1. Interference: Where there is a direct flight between organisms for resources, it is called interference. For example: when animals protect their food from other animals, for best survival.

2. Exploitation: It is a condition when an organism uses all resources, leading to depletion of resources for other animals. Such a condition is known as exploitation. In this condition, there is a direct fight for resources. It is a natural phenomenon and leads to the evolution of organisms. 

3. Ecological Niche: The niche is the way of life of a species marked by the set of conditions, resources and interactions it requires. Every species has its own capacity to fit in its ecological community and have a tendency to tolerate various environmental factors to a certain extent. Example: Species of fish is classified on the basis of specific salinity range, pH level and also the type of food they consume.  

In case, if two organisms have the same niche, then it is very difficult to survive in the same environment due to the presence of competition between them. 

4. Resource Partitioning: In case if one or both the species belong to the same niche, then they undergo evolution to use their resource in different ways or they develop best feeding habits for best survival and by this method competition exclusion can be avoided. As such, the evolution process leads to non-overlapping of resources resulting in different niches. By this process, it becomes easy to exist together. 

For example, Anole lizards are found in large numbers in the Island of Puerto Rico. These lizards evolved over time due to the natural selection process and they got further differentiated into 11 more new species that use different kinds of resources and also live in different habitats. This is the example of resource partitioning. 

MCQs:

1. The Principle of Competitive Exclusion Was Stated By:

A. G. F. Gause

B. Darwin

C. Robert Hooke

D. Robert Brown

2. Which of the Following Best Describes an Ecological Niche?

A. A cramped, small habitat

B. A hole in the food chain

C. An organism’s role in its ecosystem

D. The losing species of competitive exclusion